Medical procedures that require tracking of the position of a lesion or device in the human body are very common. A lesion is referred to herein as a tumor, diseased artery or any other diseased or target tissue. For example, in percutaneous coronary intervention (PCI) procedures a balloon is inserted through a catheter from an artery in the groin to a narrowed section in a coronary artery. The balloon is then inflated, compressing the plaque and dilating the narrowed coronary artery so that blood can flow more easily. This is often accompanied by inserting an expandable metal stent.
The procedure is monitored by X-Ray imaging technique referred to as angiography, which combines fluoroscopic projection imaging of multiple images per second and infusion of contrast agent (also referred to as dye) to the arteries to be viewed. Using angiography, the physician can view and identify the narrowing in the artery, direct the balloon and stent to position and verify correct positioning of the stent.
However, conventional fluoroscopy or angiography provide 2D projection images and do not disclose the complete 3D structure underneath. The 3D structure of human organs can be viewed by techniques such as Computed Tomography (CT) or MRI.
CT scanners are used routinely in medical, homeland security and other fields. In a typical CT scanner there is an X-Ray source and array detector, both mounted on a gantry and made to rotate about a scanned subject. Radiation that was attenuated by the scanned subject is received by the detector, acquired and reconstructed to produce images of tomographic cross sections, also called “slices”. The slice images are stored on computer media, displayed and optionally processed to 3D images.
CT scanners can acquire, reconstruct and display single or several slices in almost real time. However, CT scanners typically require minutes to scan a whole organ, reconstruct the slice images and process the data to 3D presentation. Therefore, CT scanners cannot typically be used for real time monitoring of position in three dimensions during interventional procedures.
One solution known in the art is to carry out a CT scan of the subject and generate volumetric images. Subsequently, in a different session using a different system, real time 2D fluoroscopy or other real time imaging is performed wherein the CT images are used as a guiding roadmap. Some exemplary clinical applications where combination of 2D fluoroscopy and 3D CT images may be beneficial are neural interventions and electrophysiology interventions such as RF ablation and lead placement procedures. The disadvantage is that the two sets of images are not acquired under identical conditions of the scanned subject and are not registered respective of each other in space, thereby limiting the accuracy.
CT scanners using a cone beam X-Ray source and a large area array detector are also known in the art. It has been noted that the large area CT detector can be used in association with the cone beam source to generate fluoroscopic or angiographic 2D images. Substantially the method involves positioning the gantry carrying the source and detector at a given rotation angle wherein the subject is in the radiation field, acquiring attenuation data, processing the data and displaying multiple 2D images per second.
U.S. Pat. No. 6,198,790 to Pflaum et al., the content of which is incorporated herein by reference, discloses an X-ray diagnostic apparatus having a computed tomography device including a first X-ray tube, which is fastened to a gantry ring and which emits a fan-shaped effective beam, and an opposed radiation receiver, which is formed by a row of individual detector elements, each of which forms an electrical signal corresponding to the received radiation intensity. A second X-ray tube is additionally fastened to the gantry ring at a right angle to the first X-ray tube, opposite which, at the gantry ring, a matrix-like X-ray detector is arranged. The second X-ray tube is activated in specified rotational positions in pulsed fashion, such as at the uppermost rotational point. X-ray shadowgraphs thus can be produced simultaneously with CT images and without a need for repositioning any of the apparatus components.
U.S. Pat. No. 7,164,745 to Tsuyuki, the content of which is incorporated herein by reference; discloses X-ray computed tomography apparatus for medical diagnosis, reconstructs tomographic image based on detection of X-rays penetrated through patient, and creates fluoroscopic image on plane that is perpendicular to X-ray path.
CT scanners using multiple cone beam sources are also known in the art. Multiple X-Ray sources may be distributed azimuthally about the rotation axis, or along an axis parallel to the rotation axis (Z axis), or both. Of interest to us are configurations wherein the sources are relatively close to each other and are irradiating a common detector array such that the multiple beams are at least partially overlapping.
Some disclosures that cover such geometries are application U.S. Publication No. 2006/285633 A1 to Sukovic et. al.; PCT Publication Nos. WO 2006/038145 A to Koken et al. and WO 2008/122971 A1 to Dafni, and which is assigned to the assignee of the present invention, the content of which is incorporated herein by reference.
It has been noted that overlapping beam from multiple X-Ray sources operating asynchronously can be used for stereoscopic visualization. Some disclosures are U.S. Pat. No. 5,233,639 to Marks; U.S. Pat. No. 4,819,255 to Sato; U.S. Pat. No. 4,712,226 to Horsbaschek; and U.S. Pat. No. 6,181,768 to Berliner, the contents therein are incorporated herein by reference. Several publications discuss X-Ray stereoscopic imaging in connection to angiography: “Machine precision assessment for 3D/2D digital subtracted angiography images registration”, Proceedings of SPIE Medical Imaging 1998, K. Hanson Ed, vol 3338, pp. 39-49, 23-26 Feb. 1998, and “Application of Stereo Techniques to Angiography: Qualitative and Quantitative Approaches” Jean Hsuy et. al., Purdue University, all incorporated herein by reference.
However, devices incorporating the 3D imaging capabilities of CT scanners and stereoscopic fluoroscopy or angiography in the same system are not known in the art. It is the purpose of this invention to provide such a device and thereby gain the benefits of accurate spatial registration between the two sets of images, as well as the benefits of an efficient clinical workflow.